"To them, I said, the truth would be literally nothing but the shadows of the images."
- Plato: The Allegory of the Cave
"Achilles: Was it (a sound record) a present for the Crab?
"Tortoise: Absolutely! I suggested that we listen to it on his new phonograph ... So he put it on. But, unfortunately, after only a few notes, the record player began vibrating rather severely, and then with a loud "pop", broke into a large number of fairly small pieces, scattered all about the room."
- Dialog Contracrostipunctus in "GEB" by Douglas Hofstadter
Mass-spring system and Hooke's Law. Concept of restoring force.
Vibrating motion. Period and frequency of vibrations.
Pendulum. Conservation of energy in mass-spring system and pendulum. Speed as a function of position.
Reference circle. Motion of a shadow and its similarity to mass-spring system and pendulum.
Simple harmonic motion (SHM). Periods of vibrations for the mass-spring system and pendulum.
Plato's "Allegory of the Cave".
Equations for displacement/position and velocity in SHM. Solutions of the differential equation of SHM. Amplitude and phase.
Damped oscillations.
Vibrations under influence of external periodic force. The phenomenon of resonance. Resonant frequency.